“One outcome of the study is that we now have an estimate of what an average freeze event costs us in yield—at least an 8 bushels per acre reduction,” Holman said, adding that average reduction is probably more than that. The experiment stations did not report very poor years with freeze damage.

“The results suggest that future wheat breeding and cropping systems research should work to improve stand establishment and minimize freeze injury,” he said.

Because the main effect of irrigation was significant for this study, the scientists analyzed the data separately for irrigated and non-irrigated experiments.

Holman acknowledged that the effect of monthly temperature and precipitation on wheat yield is not fully understood. The study indicated, however, that warm weather in fall (October-November), early spring (April), and June tend to reduce yields. Warm late-spring temperatures tend to increase yields.

That could be because warm fall temperatures cause more fall growth, he said. If the growth gets excessive, it can deplete soil moisture, increase susceptibility to freeze injury, increase insect and weed problems, and increase spring lodging – all of which can reduce yield potential.

“Warm early-spring (April) temperatures can cause wheat to break dormancy and initiate spring growth too early, which can result in freeze injury,” Holman said.

Warm late-spring (May) temperatures increase wheat growth and development, enabling the plants to initiate anthesis (flower opening) and maturation during a cooler period of the year. But, warm June temperatures increase leaf post-maturity senescence and reduce kernel fill, which ultimately can curb yield.